Add initial support for code metadata (#1840)

See https://github.com/WebAssembly/tool-conventions/blob/main/CodeMetadata.md  for the specification.

In particular this pr implements the following:

- Parsing code metadata sections in BinaryReader, providing appropriate callbacks that a BinaryReaderDelegate can implement:
    - BinaryReaderObjdump: show the sections in a human-readable form
    - BinaryReaderIr: add code metadata in the IR as expressions
- Parsing code metadata annotations in text format, adding them in the IR like the BinaryReaderIR does
- Writing the code metadata present in the IR in the proper sections when converting IR to binary
- Support in wasm-decompiler for showing code metadata as comments in the pseudo-code

All the features have corresponding tests.

Support for code metadata is gated through the --enable-code-metadata feature. For reading/writing in the text format, --enable-annotations is also required.

Missing features:

    Support for function-level code metadata (offset 0)
    Extensive validation in validator.cc (like making sure that all metadata instances are at the same code offset of an instruction)

1 files changed, 15 insertions, 0 deletions

diff --git a/src/ir.h b/src/ir.h
index 5974f64f..01a2bf57 100644
--- a/src/ir.h
+++ b/src/ir.h
@@ -320,6 +320,7 @@ enum class ExprType {
   Call,
   CallIndirect,
   CallRef,
+  CodeMetadata,
   Compare,
   Const,
   Convert,
@@ -631,6 +632,19 @@ class CallIndirectExpr : public ExprMixin<ExprType::CallIndirect> {
   Var table;
 };
 
+class CodeMetadataExpr : public ExprMixin<ExprType::CodeMetadata> {
+ public:
+  explicit CodeMetadataExpr(std::string_view name,
+                            std::vector<uint8_t> data,
+                            const Location& loc = Location())
+      : ExprMixin<ExprType::CodeMetadata>(loc),
+        name(std::move(name)),
+        data(std::move(data)) {}
+
+  std::string_view name;
+  std::vector<uint8_t> data;
+};
+
 class ReturnCallIndirectExpr : public ExprMixin<ExprType::ReturnCallIndirect> {
  public:
   explicit ReturnCallIndirectExpr(const Location& loc = Location())
@@ -846,6 +860,7 @@ struct Func {
   LocalTypes local_types;
   BindingHash bindings;
   ExprList exprs;
+  Location loc;
 };
 
 struct Global {